Research On Ultrafast Tm:YAG Solid Laser Technology Based On MoS₂ Material

The 2?m band ultrafast laser is located in the atmospheric window band,which has strong absorption for water molecules and human tissues.The diode laser end pumped 2?m ultrafast all solid-state ultrafast laser has the advantages of simple structure,high efficiency,high stability,long life,large output energy,high peak power,good beam quality,and is widely used in scientific research,industry,military,medical and other fields Including material processing,high field physics,time-resolved spectroscopy,nonlinear optical frequency conversion and medical diagnosis.Mode locking technology is an effective way to obtain ultrashort pulse laser,laser crystal is an essential optical device to achieve solid-state laser output,and saturated absorption material is the core component to obtain ultrashort pulse laser.The main work of this paper is from two aspects of theory and experiment The passive mode-locked Tm:YAG laser technology is studied around MoS₂ material.Firstly,the absorption and fluorescence spectrum characteristics of Tm:YAG crystal are studied,and the absorption and emission cross-section parameters of the crystal are studied according to the spectrum characteristics of the crystal,which provides the basis for the laser output of Tm:YAG laser.Based on the study of spectral characteristics,the rate equation theory of Tm³⁺two-level system is studied,the mechanism of 2?m band output of Tm:YAG crystal is revealed,and the influence of matching mode of pump light and oscillating light on laser characteristics is explored.Secondly,the physical properties of the two-dimensional transition metal sulfide material MoS₂ and the corresponding saturated absorption preparation technology were studied.The characterization technology of MoS₂ saturable absorber is explored in depth,and the necessary parameters of MoS₂ saturable absorber as mode-locked device are obtained by means of Raman spectrum,scanning electron microscope and transmission electron microscope.The nonlinear absorption characteristics of the saturable absorber are studied in depth by pumping MoS₂ saturable absorber with 2?m pulse laser,and the important nonlinear parameters of the saturable absorber are obtained the degree and harmonic original transmittance were 37.94 m J/cm²,2.9%and89.2%respectively.Finally,on the basis of theoretical research,the passively Q-switched and passively mode-locked Tm:YAG lasers with MoS₂ as saturable absorber are studied.In the process of the study of passive Q-switched Tm:YAG laser,the output characteristics of two mirror flat cavity CW and passive Q-switched Tm:YAG laser are studied,and the saturated absorption characteristics of MoS₂ material are verified.In the passive Q-switched mode,the pulse width of Tm:YAG laser is 655 ns at118.6KHz repetition rate,the maximum average output power is 1327m W,and the corresponding beam quality factors are 1.16 and 1.19.In the research process of passive mode-locked laser,the output performance of folded cavity passive mode-locked Tm:YAG laser is studied deeply,and the laser has achieved high efficiency.In passive mode-locked mode,the repetition frequency of Tm:YAG laser is set as 232.2 MHz,the signal-to-noise ratio of laser output is 43.6 d Bm,the shortest pulse width is 280ps,the maximum average output power is 200 m W,and the corresponding output beam quality factors are M_x²=1.06 and M_y²=1.02.